Thread: Need help adjusting spindle bearings on 10k

I'm going through "the manual" working on rebuilding my SB 10K... today I'm at the part of re-assembling & adjusting the spindle bearings and I'm not sure I have it right.

I'm using a Starret digital .0001" indicator and a Mitutoyo .00005" digital indicator so I don't think I'm getting "error" in my readings.

Right now as it is set I have .0009" on the in-board end of the spindle and .0013" on the out-board end of the spindle. My problem is, to get the numbers even close to those numbers the spindle went from "free-turning" to turning with "a lot" of resistance. I know it's very hard to quantify how much resistance there is in words, but I will try. I can grab the out-board end where the reversing gear meshes with one hand and turn the spindle with only a little effort but it stops quickly when I let go.

Assuming a few rotations wouldn't hurt at this point I plugged it in to see if it spun easily under power, and it did. It continues about 2-3 rotations after power is cut (no chuck on the spindle).

Are my bearings too tight? Or is this much resistance normal?

Also, if I tighten the outboard end down a bit more it locks the spindle. I think .0013" is "close-enough". Do you agree? Or is there something wrong?

The bearings looked ok when I had it apart. A couple "oh crap" marks on them from a previous "rebuild" by somebody that didn't know what they were doing (previous owner) but the spindle looked fine and the marks are only comsetic for the most part. It was obviously run after these marks were put in the bearings and it didn't harm the spindle.

Thanks for your help!!!

very easy to get false readings when setting clearances- for a lot of reasons.

i don`t even use an indicator nowdays- much easier to just remove shims until you get drag- then add .002

contrary to popular belief, super tight clearances on a plain bearing machine does not improve performance.

You could try a different oil for the spindle to see if that helps. I've found the spindle runs more freely if I use Mobil-1 5w20. But remember that when the bearings are properly set, the spindle is supported by an oil film and a viscous film such as oil adds a fair amount of rotation resistance even though the bearings are not making metal contact. Rotation should be smooth but not necessarily as free as you might expect from ball bearings.